You need to change the "Game name" in the vehicles.ide eg.
pstockade, pstockade, car, STOCKADE, PSTOCK
pstockade, pstockade, car, (handling), (game name)
So if you want your pstockade to sound and act like a crown vic, go for
pstockade, pstockade, car, POLICE, POLICE,
if you want it to sound/handle like an SUV, try
pstockade, pstockade, car, POLPAT, POLPAT,